The present invention relates to the production of concrete compositions having improved characteristics and containing glass, including ordinary recycled glass. In particular, the invention relates to concrete compositions having glass aggregate, including coarse and fine glass aggregate. The present invention also relates to compositions containing E-glass (also known as electric glass). Processes for producing the compositions of the invention are also provided.
Due to recent interest in recycling and improved collection for recycling of glass, a significant surplus of recycled glass has accumulated. A substantial amount of such glass is simply land-filled, there being no significant economic motive for its further use. Significant amounts of glass byproducts are also generated from certain manufacturing processes which are not readily disposed of, or productively utilized.
A number of attempts have been made to successfully use glass as an additive in concrete compositions. Certain compositions proposed have been successful in accomplishing specific goals. For example, U.S. Pat. Nos. 5,803,960 and 5,810,921 to Baxter, describe the addition of lithium-containing and chromium-containing glass, respectively, in order to overcome alkali-silica reaction (ASR) in concrete compositions. The glass compositions disclosed, however, are specifically directed to the suppression of ASR, and must be specially formulated. Glass compositions containing zirconia have also been suggested as alkali-resistant glass components of cement compositions (glass fibersxe2x80x94U.S. Pat. No. 5,912,361, to Molloy et al.). Other forms of specially treated glass fibers for concrete reinforcement have also been suggested, as have certain specialized compositions containing very fine silica particles or silica dust, e.g. as disclosed in U.S. Pat. No. 4,385,935, to Skjeldal (reissue Re. 32,742).
Desired characteristics of a general use concrete composition include adequate strength, a reasonable open time (time from pouring to irreversible set), decreased slump, decreased splash, decreased creep, a thixotropic character during open time allowing re-working of the initial set using vibration of the mixture, decreased bleed, and increased density and water impermeability.
Certain applications may require concrete compositions possessing further special characteristics. One example is the application of concrete compositions to form the areas adjacent to, or inside of, swimming pools or other outdoor recreational areas. It is desirable to produce a composition which may be effectively xe2x80x9cwashedxe2x80x9d after pouring, such that an increased amount of surface area is actually comprised of exposed aggregate component surfaces. This reduces the temperature experienced when such surfaces are contacted, e.g. by bare feet of persons utilizing the area around a swimming pool. Accordingly, it would be desirable to formulate a cement or concrete composition which exhibits superior characteristics particularly applicable to such uses. Such characteristics include superior workability, as discussed above, and characteristics compatible with the particular processes for preparing surfaces of such outdoor recreational areas.
Accordingly, it would be very desirable to produce a concrete composition possessing these desired characteristics by utilizing a glass component capable of having the ordinary composition of recycled glass, or utilizing a glass component derived from an industrial byproduct.
E-glass, also referred to as electric glass, is a type of borosilicate glass. E-glass is typically produced as a fiber component, e.g. for use in reinforced plastics utilized in applications requiring a high degree of electrical resistivity. The production method generally utilized results in a substantial amount of waste which is unusable in the standard application. Therefore, the use of E-glass in an improved concrete composition also would also provide a productive use for waste E-glass, as well as imparting superior characteristics to such compositions. Accordingly, it would also be desirable to produce a concrete composition having improved characteristics which includes in its composition a component comprising E-glass. In addition, it would also be desirable to provide a process wherein an E-glass component may be added to a general processing operation to producing a cement or concrete composition suitable for transport or immediate use.
The present invention provides cement and concrete compositions having improved characteristics which contain glass, including recycled glass as well as compositions containing E-glass. The invention also relates to methods for producing the concrete compositions of the invention. The concrete compositions of the invention are particularly useful because they exhibit adequate strength, a reasonable open time (time from pouring to irreversible set), decreased slump, decreased splash, decreased creep, a thixotropic character during open time allowing re-working of the initial set using vibration of the mixture, decreased bleed, and increased density and water impermeability.
The present invention also provides a use for, and means of disposal of, both recycled glass and waste E-glass. The recycled glass used in particular compositions of the invention is not of any specialized glass composition, nor is it specially treated. Further, the invention provides a process for producing E-glass containing cement or concrete compositions wherein the E-glass component is added prior to a general processing operation in the production of the cement or concrete compositions. Such a process increases the efficiency of the production of composition of the invention in a form suitable for transport, storage or immediate use.
In one aspect, the present invention relates to a concrete composition comprising glass particles, cement, and aggregate, wherein the size of the glass particles comprises a graded particle size distribution from about 100 mesh to about 325 mesh.
In another aspect, the invention relates to concrete composition comprising glass particles, cement, blast furnace slag and aggregate.
In another aspect, the invention relates to a concrete composition comprising glass particles, cement, fly ash, and aggregate.
In another aspect, this invention relates to a concrete composition comprising glass particles, cement, metakaolin, and aggregate. In another aspect, this invention relates to a concrete composition comprising glass particles, cement, silica fume, and aggregate.
In another aspect, the present invention relates to a cement and concrete compositions comprising glass particles, cement, a substance to mitigate alkali-silica reaction (ASR), and aggregate, wherein the size of the glass particles comprises a graded particle size distribution from about 100 mesh to about 325 mesh.
In another aspect, the present invention relates a composition comprising E-glass particles, cement, and aggregate, wherein the size of the E-glass particles comprises a maximum particle size of from about 270 to about 325 mesh.
In another aspect, the present invention relates a composition comprising E-glass particles, cement, and aggregate, wherein the size of the E-glass particles comprises a particle size of from about 4 to about 325 mesh.
In yet another aspect, the present invention relates to a concrete composition comprising a glass aggregate, cement, and E-glass particles.
In another aspect, the invention relates to methods of producing the cement and concrete compositions of the invention.
In order to produce a cement or concrete composition having desirable characteristics for forming surfaces for outdoor recreational areas, such as areas adjacent to, or inside of, swimming pools, the glass particles of the invention may be combined with cement, aggregate and a substance known in the art to reduce the phenomenon of alkali-silica reaction or ASR. Addition of such a substance is generally necessary in these applications due to the use of reactive aggregate in the final compositions. Significant advantageous properties are achieved by combining cement and aggregate with the glass particles as described and an effective amount of lithium-containing glass (see U.S. Pat. No. 5,803,960 to Baxter), or other substances known in the art to mitigate ASR. Also, substitution of a portion of the cement with E-glass particles allows utilization of glass as an aggregate by preventing the usual ASR expansion problems associated with use of glass aggregates in concrete.
The concrete compositions of the present invention flow only on demand, exhibit superior workability, and can be vibrated to activate the thixotropic character of the composition without segregation of the materials. The compositions of the invention are especially useful on steep slopes due to the reduced tendency to exhibit creep. The compositions also place less stress on forms and the forms may be stripped sooner. The compositions can also be pumped with lower slump than standard concrete and may be pumped under water with less segregation than standard compositions. The low slump compositions of the present invention also finish easier and smoother that standard concrete having similar slump characteristics. The compositions of the invention also exhibit less bleed water and the mix water remains in the composition, allowing it to be finished faster. Vibrating or manual manipulation causes the compositions to remain open for working longer (increased thixotropic character), however, once manipulation is stopped, the compositions becomes very stable allowing forms to be removed sooner.
The E-glass-containing compositions of the invention are particularly useful as pool plasters in the construction of swimming pools. These compositions have superior workability as described above. The E-glass also acts as a pozzolan and does not contribute to ASR. It increases flow, controls creep, and increases workability while controlling bleed water and shrinkage. The E-glass-containing compositions of the invention are also particularly useful as grouts or mortars.
The present invention, and preferred embodiments thereof, are described in more detail below. Although the present invention has been described with reference to certain embodiments, other embodiments may achieve similar results and advantages. Variations and modifications of the present invention will be apparent to one skilled in the art and the disclosure herein is intended to cover all such modifications and equivalents.